The membrane protein embedded in a cell membrane, called an “ion channel”, is an important protein relating to the signal transmission in a biological system. In measurement of the function of an ion channel and drug development using this function, measurement of the current flowing through the ion channel is sought. In response to this demand, the patch clamp method was developed as art for measuring the ion channel current was.
The pipet patch clamp method was first developed as the patch clamp method, but there was the problem that the ion channel current of cells could only be recorded at a single point and therefore application to high throughput screening by multipoint measurement was not possible. As art for solving this problem, the planar patch clamp method was developed. The planar patch clamp method, for example, as disclosed in Japanese Patent Publication No. 2003-511668A (PLT 1), Japanese Patent Publication No. 2005-536751A (PLT 2), etc., provides a plurality of fine through holes in a silicon chip or other solid substrate, places cells on the individual through holes, and uses electrodes to measure the ion channel currents of the cells thereby enables measurement of the ion channel currents at multiple points. Specifically, the ion channel currents are measured by placing a bath solution around the cells on the substrate and a pipette solution at the lower side of the through holes of the substrate, placing electrodes (upper electrode and lower electrode) electrically conductive with the bath solution and pipette solution, respectively, and applying membrane potential between the electrodes.
The inventors have proposed various improvements to the planar patch clamp method up to now. For example, Japanese Patent Publication No. 2009-204407A (PLT 3) and Urisu et al., Analytical and Bioanalytical Chemistry, (2008), 391: 2703-2709 (NPLT 1) disclose a culture type planar patch clamp device setting an extracellular matrix-forming substance at the rims of the through holes of the substrate so as to extend the lifetimes of the cells arranged at the opening parts of the through holes and culturing the cells while measuring the ion channel currents. The pamphlet of International Patent Publication No. 2013/094418 (PLT 4) discloses a planar patch clamp device using electrode parts obtained by making the electrode container ends out of an inorganic porous material and sealing in a saturated electrode solution (salt bridge type electrode parts) to prevent fluctuations in membrane voltage, reduce noise, and improve the precision of current measurement. International Patent Publication No. PCT/JP2013/57976 (WO2014/045618: PLT 5) describes forming cell fixing locations surrounded by protrusions at a cell arrangement region including through holes on a cell culture substrate, thereby limiting the movement of nerve cells while forming a nerve cell network and improve the precision of current measurement.